Regardless of whether it is for food use or industrial use, ethanol is a substance that can be used for various applications. Chemically-synthesized ethanol and fermented ethanol by yeast etc. have been used for industrial use and for food use respectively. Especially, recently, because of the development of biotechnology and increasing awareness for biomass utilization, attempts to use fermentative production not only for food use, but also for industrial use, in particular, for fuel ethanol are increasing. The technology of fermentative production using yeast for ethanol production has been used through the ages, and a number of improvements aiming to enhance productivity of yeast which has an important role therein are disclosed.
Use of thermophilic microorganisms can be exemplified as one improvement of fermentative production using microorganism for industrial application. Since generation of heat (fermentation heat) associated with fermentation process reduces life activities such as metabolism of non-thermotolerant microorganism and may lead the microorganism to death, solutions have been taken, for example, by installing a cooling device, in particular, when a large fermenting vessel is used for fermentation. However, cooling devices have drawbacks, such as cost problems etc., and in enzyme chemistry, if fermentation under a high temperature condition is realized, a more effective fermentative production can be expected. Therefore it is effective to isolate a microorganism having both thermotolerance and fermentative ability from nature, or to confer thermotolerance to a fermentative microorganism by genetic recombination. From this viewpoint, various thermotolerant (thermophilic) microorganisms and technology of fermentative production by utilizing the same are disclosed, and examples include a method to confer thermotolerance by introducing a gene of thermophilic methane bacterium, thermophilic bacillus, thermophilic fiber-degrading bacterium, thermophilic thermoactinomyces, or hyperthermophilic archaea into a microorganism of another species; a method for expressing a thermotolerance-related gene of thermophilic bacterium in Saccharomyces yeast; and a method for producing ethanol by using Kluyveromyces marxianus, a yeast fermentable at high temperature, etc. (Patent Documents 1 to 8). However, the above inventions relate to production of a substance using mainly a thermophilic bacterium, and they had drawbacks, for example, in that the productivity of ethanol is reduced in the case of yeast which thermotolerance is improved. Thus, the development of a thermotolerant microorganism applicable to the technology of fermentative production of ethanol in which exploding demands are predicted hereafter was awaited.
Patent Document 1: Published Japanese translation of PCT international publication No. 2003-520045; “METHOD AND DEVICE FOR PRODUCING BIOGAS, WHICH CONTAINS METHANE, FROM ORGANIC SUBSTANCES”
Patent Document 2: Published Japanese translation of PCT international publication No. 2006-514831; “PREPARATION OF LACTIC ACID FROM A PENTOSE CONTAINING SUBSTRATE”
Patent Document 3: Japanese Laid-Open Patent Application No. 5-336951; “THERMOPHILIC CELLULOSE-DECOMPOSING BACTERIUM”
Patent Document 4: Japanese Laid-Open Patent Application No. 6-303968; “THERMOPHILIC ACTINOMYCES”
Patent Document 5: Japanese Laid-Open Patent Application No. 2000-050894; “A METHOD FOR PRODUCING FERMENTATIVE PRODUCTS AND STRESS-TORELANT MICROORGANISMS”
Patent Document 6: Japanese Laid-Open Patent Application No. 2001-069979; “A METHOD FOR PRODUCING L-GLUTAMINE THROUGH FERMENTATION PROCESS”
Patent Document 7: Japanese Laid-Open Patent Application No. 2006-280253; “A YEAST MUTANT STRAIN CAPABLE OF HIGHLY PRODUCING HEAT-RESISTANT ENZYME”
Patent Document 8: Japanese Laid-Open Patent Application No. 63-42690; “A METHOD FOR PRODUCING ETHANOL USING A YEAST WHICH IS FERMENTATIVE AT HIGH TEMPERATURE”
Non-Patent Document 1: Kourkoutas Y. et al. 2002. Bioresource Technology 82, 177-181.
Non-Patent Document 2: Yarrow D., et al. 1998. The Yeasts, A Taxonomic Study 4th edition. Elsevier, Amsterdam. pp. 77-100.
Non-Patent Document 3: O'Donell K. 1993. Fusarium and its near relatives. CAB International, Wallingford. pp. 225-233.
Non-Patent Document 4: Bergmeryer H. U. 1974. Methods of Enzymic Analysis, Vol. 1. Verlog Chemic Weinheim and Academic Press, New York-London.
Non-Patent Document 5: Adachi et al. 1978. Agric Biol. Chem. 42, 2045-2056.